Adaptive Multi Rate AMR voice coding is the most common voice coding on modern mobile networks it provides very good quality voice packed into 12 Kbps. This compares to 64 Kbps non compressed PCM (ITU-T Rec. G.711) used in fixed networks. AMR also supports lower bit rates for useful but poorer quality voice yielding more capacity or in some cases some voice communications in dire radio propagation conditions.
W-AMR or Wideband AMR coding is a newer standard which was introduced into GSM and WCDMA with 3GPP Release 5 and provides double the voice bandwidth (50 to 7000Hz) compared to AMR (300 to 3400Hz) using 12.65 Kbps. It also offers 8.85 and 6.6 Kbps coding options for use during adverse radio conditions or to temporarily increase networks voice capacity.
The W-AMR capability needs to be implemented in both the network and the phone. The GSM Association gsmcom.com reported in June 2014 that 109 operators in 73 countries support W-AMR and the new mobiles from the most popular makers like Samsung, Apple HTC and Nokia support W-AMR out of the box. As well the calling and called phone need to be W-AMR capable to get the highest quality voice call. Calls to non W-AMR capable mobiles and to or through the fixed network are limited by the 3,400 Hz G.711 bandwidth. There will be some improvement in quality of a one end W-AMR call due to improved echo and background noise supression capability built into the newer coding.
Telstra launched W-AMR on NextG in June 2011 and it reports that it is now seeing large increases in the volume of calls able to enjoy the higher quality. W-AMR would be of particular benefit to professional broadcasters, businesses using mobile for voice conferencing as well as normal users calling in noisy locations. You can see a demo of W-AMR by Martin Stanford on the (then) Orange Network in the UK here.
You can see GSA’s information on W-AMR here. Note you will have to register first using the link on site.